1. Field of the Invention
The invention relates to field emission display devices and, more particularly, to a pixel tube for a field emission display device.
2. Discussion of Related Art
Field-emission illumination/display devices are based on emission of electrons in a vacuum. Electrons are emitted from micron-sized (or less) tips in a strong electric field, and the electrons are accelerated and collide with a fluorescent material. The fluorescent material then emits visible light. Such field emission devices are thin, are light weight, and provide high levels of brightness.
Conventionally, a material of the tips has generally been selected from the group consisting of molybdenum (Mo) and silicon (Si). With the development of nano-technology, carbon nanotubes (CNTs) have also been used for the tips of the field emission devices.
A conventional pixel tube includes a cathode electrode and an anode electrode arranged over the cathode electrode. The cathode electrode includes a CNT yarn used as an emitter. The anode electrode is generally a transparent conductive layer disposed on a substrate. At least one fluorescent layer is formed on the anode electrode and faces the CNT yarn. In operation, electrons emitted from the CNT yarn are, under an electric field applied by the cathode electrode and the anode electrode, accelerated, and then collide with a fluorescent material of the fluorescent layer. The collision of the electrons upon the fluorescent layer causes such layer to fluoresce and thus emit light therefrom. The CNT yarn has an excellent electric field electron emission efficiency to thereby obtain a large emission current at a low applied voltage.
However, the fluorescent layer tend to directly experience the large emission current at a low voltage, which can greatly decrease the irradiance efficiency of the fluorescent. Moreover, the collision of electrons of large emission current can potentially damage the fluorescent material. Thus, the life of the pixel tube can be compromised.
What is needed, therefore, is a pixel tube for a field-emission illumination/display device that operates at a high voltage to obtain a small emission current and that has a long lifetime.